1. Field
The present invention is directed to a light guide one or both surfaces of which are structured, and a method and an apparatus for manufacturing the same. The present invention is also directed to an illuminating system using the light guide one or both surfaces of which are structured.
2. Background
An illuminating apparatus using an optical guide by which a light can be transmitted to far distance with relatively small transmission loss is known in the art. The optical guide is also called as a light conduit, a light pipe, or a light tube, and is used for effectively distributing a decorative or functional light over a relatively large area.
As well known in the art, the optical guide can get by roll-working an optical lighting film made of transparent polymer material in a tube form, and fixing it inside a transparent acryl pipe. The optical lighting film includes a smooth inner side not structured and an outer side structured with linear prism arrays forming a plurality of triangle grooves along with a certain direction. According to the above structural feature, the optical guide transmits a light in the longitudinal direction of the optical guide by which a light inputted into the optical guide within certain angle is restricted to inside the optical guide by inner total reflection. The typical optical guide like the above is disclosed in U.S. Pat. No. 4,805,984, which was cited in this application as reference.
Below, the principles of light transmission and reflection of the optical guide having the above construction will be explained in the scope necessary to understand the present invention with reference to the drawings.
FIG. 1A is a cross-sectional view illustrating a part of an optical lighting film to describe transmission and reflection in an optical guide of an illuminating system in the art. And, FIG. 1B is a perspective view illustrating a part of an optical lighting film to describe transmission and reflection in an optical guide of an illuminating system in the art. But, for convenience's sake, in the figures, unstructured inner side is upper side, and structured outer side is lower side.
Referring to FIG. 1A and FIG. 1B, a light from a light source (not shown) is incident and refracted to an unstructured inner side of the optical lighting film (point 1), total-reflected on both sides of a prism of the structured outer side (point 2 and point 3), whereby the light proceeding to outside is refracted at the inner side (point 4), and is inputted again to inside, as shown by the arrow. As this total-reflection process is repeated, the light is substantially proceeding along with the longitudinal direction of the optical guide. Thus, the transmission ability of a light generated from the light source can be enhanced by using the optical lighting film.
The illuminating system in the art like the above improves the transmission ability of a light generated from a light source by using the optical lighting film, but there was a wide difference in luminance between far distance and short distance from the light source. That is, it was difficult to properly control the light transmission inside the optical guide and the light emission to outside, and so difficult to obtain uniform brightness in the longitudinal direction of the optical guide in the illuminating system in the art.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.